In a semiconductor device manufacturing process, a cobalt film is considered as a seed of Cu wiring or as a contact with Si in a MOS type semiconductor. As for a method for forming a cobalt film, there is known a chemical vapor deposition method (CVD method) using an organic metal compound gas (see, e.g., Japanese Patent Application Publication No. 2011-63848).
Recently, cobalt attracts attention as an alternative for tungsten which is filled in a via hole or the like.
However, in the case of forming a cobalt film by CVD using an organic metal to fill a via hole as disclosed in Japanese Patent Application Publication No. 2011-63848, a seam that is a space where no film is formed may be generated in the cobalt film. This is because a film forming rate near an opening of a hole is greater than a film forming rate at a bottom of the hole.